Bending performance of cross-laminated timber constructed from fibre-managed Eucalyptus nitens under short-term and long-term serviceability loads

Abstract

Cross-laminated timber (CLT) has become a notable building material due to its structural efficiency, reliability and sustainability. In this study, the bending performance of three-layered CLT constructed from fibre-managed Eucalyptus nitens (E. nitens) was investigated under short-term and long-term loadings. Linear-elastic four-point bending testing was used to determine the maximum serviceability loading capacity before they reached the suggested deflection limits. A pilot study was conducted to investigate the creep behaviour of E. nitens CLT through long-term bending tests in a controlled environmental room. The study suggested that E. nitens CLT has higher serviceability loading capacity and lower creep ratio compared to CLT made from strength-class C24 spruce. The investigations of various configurations of E. nitens CLT panels based on structural grades implemented in top, cross, and bottom layers have revealed different short-term and long-term bending performances. The grade of transverse layers has been found to be the most important factor in improving the bending creep performance of E. nitens CLT. Two modelling equations were employed to perform curve fitting on the experimental creep ratio with time. The conventional power-law modelling tends to underestimate the longer-term creep ratio when compared to a recently developed nonlinear regression modelling equation that takes environmental conditions into account. The mean estimated creep ratio after 50 years was 1.77 for E. nitens CLT, and 1.89 for the C24 spruce CLT. The present study is a pilot investigation to increase the understanding of performance of the newly developed CLT made from fibre-managed plantations E. nitens, with particular emphasis on its creep behaviour. The results of this study provide valuable contributions for future research in this field, and ongoing commercial production of E. nitens CLT.